1. Field of the Invention
The present invention relates generally to substances for simulating the effect of combustion products on electronic smoke detectors and more particularly relates to an improved environmentally safer formulation.
2. State of the Prior Art
Smoke detectors are commonplace fixtures in public buildings and private dwellings to protect lives and reduce property damage by giving early warning of fire. Numerous lives are lost through smoke inhalation every year before the fire has spread to the rooms occupied by the victims. In a private home a properly functioning smoke detector can alert the home occupants to give them the time needed to safely exit the building. Fast response of the detector is of great importance since even one or two minutes may make the difference between a safe exit and loss of life in a typical home fire, due to the speed of propagation of the conflagration.
There are currently two basic types of smoke detectors. The ionization type senses changes in the electrical conductivity of the air in a chamber which is subject to radiation. The photoelectric type on the other hand senses light scattering in a detector chamber. Both devices respond to the presence of particulate matter or particles of combustion byproducts which, when present in great quantities, are visible as smoke. However, in the earliest stages of a fire, these combustion byproducts take the form of invisible aerosol, consisting of very fine particles suspended in air. It has been determined that such aerosols are generated at early stages of the fire, even before actual ignition, merely as a result of sufficient heating of combustible materials.
Detectors are typically provided with a "test" feature which is actuated by pressing a test button or pulling a switch mounted on the housing of the detector unit. Such "testing" however, is not a true operational test of the detector: it actually only verifies that power is supplied to the detector circuit and that the audible alarm does function. The test does not truly verify the responsiveness of the sensor element to the presence of smoke or combustion particles in the test chamber of the device. It is possible for a detector to respond as expected when the test button is pressed, while failing to respond to the presence of smoke. Smoke detectors of either type are susceptible to failure because the sensitivity of the electronic detector may deteriorate over time due to accumulation of dust, grease, corrosive fumes, moisture or other environmental contaminant. Aging of the electronic devices may contribute to such malfunctions.
For these reasons, it is desirable to provide means by which a true operational test of the smoke detector can be carried out in a convenient manner.
Operational testing of smoke detectors is described in U.S. Pat. No. 4,301,674 issued to these applicants. The Haines et al. '674 discloses a chemical formulation which, when discharged in aerosol form in the vicinity of a smoke detector, effectively emulates the presence of smoke particles. This earlier formulation is packaged in spray cans to allow easy, convenient and reliable operational testing of smoke detectors. Previous to the '674 patent, smoke detector testing was conducted either by actually generating smoke in the vicinity of the detector, or by enclosing the smoke detector in a housing to create an artificial environment into which was introduced an aerosol spray. The former approach was inconvenient and often dangerous while the latter was likewise inconvenient in that an enclosure had to be placed around the detector and furthermore, was less than a true operational test of the device in that the enclosure was often flooded with the trigger substance and consequently did not test the low level sensitivity of the device which is necessary to provide early warning of a fire.
While the '674 patent therefore represents a substantial advance in smoke detector testing, it has recently developed that certain ingredients of the formulation used in the test formulation appear to be environmentally undesirable and possibly hazardous to human health. Specifically, that formulation included three ingredients: a) hydrocarbon propellant, b) isopropyl alcohol as a carrier medium and c) dioctyl phthalate, an ester of phthalic acid, which is dispersed under pressure by the aerosol to create an aerosol effective for activating both photoelectric and ionization type smoke detectors. The formulation was dispensed from an aerosol can equipped with a finger operated dispensing valve.
Smoke detectors are usually mounted on a ceiling or high up on a wall where hot combustion gases tend to accumulate. This location places the detectors out of easy reach for the individual of average height holding a spray can in his or her hand. Often it becomes necessary to use a ladder, step stool, or the like to get adequate access. Further, the quantity of spray delivered is left to the discretion of the user. While a small discharge will usually suffice, but because a small delay is usually inherent in the detector circuit users tend to continue spraying until the detector alarm goes off. Consequently, a considerable amount of the formulation is needlessly wasted, and builds up on the housing of the detector. Also, low cost aerosol dispensers discharge a substantial volume of coarse liquid particles along with the fine aerosol mist. For test purposes, it is the aerosol mist which is desirable and effective, while the coarse spray merely wets the detector.
Further improvement is desirable in the formulation of the spray composition to make it environmentally safer and to avoid use of substances possibly hazardous to human health.